Документ взят из кэша поисковой машины. Адрес оригинального документа : http://hea.iki.rssi.ru/conf/hea2007/presentations.orig/26.12.07/chernyakova.pdf Дата изменения: Sat Dec 29 14:54:30 2007 Дата индексирования: Tue Oct 2 01:18:36 2012 Кодировка: Поисковые слова: http www.arcetri.astro.it

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M. ( / DIAS, Ireland), A. (ISDC, Switzerland)

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Key Question
Only 3 binary systems regularly observed in TeV: PSR B1259-63 (young pulsar +Be star, P=3.4 y) LSI +61 303 (comp. source + Be star, P=26.42 d) LS 5039 (comp. source + O star, P=3.9 d) Origin of the high-energy emission? Special orientation, or fundamentally different from other X-ray binaries? Powered by rotation energy rather than accretion?

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Winds collision



Equating the dynamical pressures of the winds one finds the distance to the contact surface from the pulsar. Due to the intrinsic instabilities in the winds of hot massive stars clumps may form and change the well-ordered structure, leading to the decrease of the relativistic particles escape velocity. Emission is due to the synchrotron, IC, bremsstrahlung, and proton-proton interactions.



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PSRB 1259-63
Chernyakova et al., 2006; Neronov &Chernyakova 2007

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3.4 years orbital period. e~0.87 Correlated variability with a sharp rise ( "two bumps structure" ) is seen in radio, X-ray (and TeV?) bands. Hardening of the X-ray spectrum at the disk entrance and subsequent softening on a day scale.


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IC X-ray emission
The observed spectral variability is strong argument for IC model
Eic=4[Ee/10MeV] keV tic=6x105[R/1013cm]2 [s/10keV] ts=600[B/0.1G]
-3/2 -1/2

s

[s/10keV]

-1/2

s

.... injection of electrons with energies above 10 MeV at the moment of disk entrance would result in hardening of the X-ray spectrum on a day scale. Radio and X-rays are synchrotron and IC from the same population of electrons. --> An upper limit on magnetic field B<0.1[R/1013cm] G


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TeV emission: IC, bremsstrahlung or proton-proton interactions?



The observed TeV lightcurve can be reproduced in the IC model if adiabatic loss dominates or the acceleration efficiency drops at periastron (Khangulyan et al. 06). If the matter density is n~1011cm-3, the bremsstrahlung energy loss is comparable to the IC loss (in KN regime) and proton-proton interaction time. TeV emission can be bremsstrahlung from the compact region of interaction of pulsar and stellar winds.




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LSI +61 303
Chernyakova, Neronov, Walter 2006

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ff

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Compact binary with 26.42 d orbital period. Eccentricity e~0.7 The orbital phases of radio flux maxima "drift" with superorbital period P=4.6 year. The X-ray emission peaks almost half an orbit before the radio The short scale variability is an evidence of the clumps in the wind of the Be star.


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Arguments for pulsar model
Similar to PSR B1259-63 radio and X-ray emission can be explained by the synchrotron and IC emission from the same population of the electrons. Absence of the break in the X-ray spectrum favors the "hidden pulsar" model. Extended radio source has a complicate morphology varying along the orbit (Massi et al. 2004, Dhawan et al. 2006), thus jet emission is unlikely to dominate the spectrum through the whole orbit. The pattern of the source variability in the hardness ratio vs. flux diagram is naturally explained in the compact PWN model and is qualitatively different from the pattern in conventional accreting X-ray binaries

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Structure of the Compactified Pulsar Wind Nebula
Neronov&Chernyakova, astro-ph/0701144
10 -3 Ee 10 cm t coulomb 2x10 [ ][ ]s n 10 MeV 2 L star D 10 MeV 4 t IC 10 [ 38 ] [ 12 cm ] [ ]s Ee 10 erg / s 10 3

1 G 10 MeV t s 3x10 [ ][ ]s B Ee
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2

t

diff

3x106 [

R

2 clump 11

10 cm

][

B MeV ] [ 10 ]s 1G Ee

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Lightcurves in different energy bands


Radio:


Comes from the region of the size D

~2-3x1014 cm PWN

The maximum is achieved when 10 MeV electrons efficiently escapes from the region close to the Be star Superorbital modulation is due to the Be disc precession.





X-rays:


The maximum close to the moment of the pulsar passage through the equatorial plane of the inclined disc No second maximum due to the Coulomb losses. Maximum at periastron





-rays (10 GeV): TeV:

Dip at periastron due to pair-pair production.

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LS 5039


orbital period is 3.9 d., eccentricity 0.35, at periastron R~2.2R
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Aharonian et al. , A&A 2006


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LS 5039


If LS 5039 contains young pulsars, it can not be seen because of the free-free absorption in the stellar wind No « direct proof » that the system is powered by relativistic outflow can be obtained. The nature of the compact object is not known because of the poor knowledge of the system inclination. However, « compactness » of the binary orbits gives us a chance to study the geometry of the system and to test the nature of the compact object.







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LS 5039: TeV lightcurve

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In the lightcurve drawn in terms of the « true anomaly » instead of the « orbital phase » the two peaks become equidistant from the inferior conjunction!


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« Rotating hollow cone » model
Neronov&Chernyakova, ApJ 2008 (astro-ph/07113085)

The symmetry of the phases of the maxima w.r.t. the the inferior conjunction has a geometrical explanation, similar to the explanation of the two peaks of the folded lightcurves of pulsars. The origin of the holow cone is due to the angular dependence of the -ray production rate and absorbtion coefficient (Dopler effect).


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Constraint on the geometry



If i>/2-0- then the direction of the line of sight passes through the "wall" of the cone twice per orbit (=atan(h/D)) Maxima are located at 1,2=inf +/- , =acos{1-[sin(i+)-cos0]/cos sin(i)} Thus if the source is located in the orbital plane (=0), then the inclination i>400. If the inclination is small, then source is located above orbital plane, e.g. i~250, >150






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Conclusions

-ray loud binaries apparently form a separate class of sources powered by interaction of relativistic wind from the compact object with the stellar wind.

The emission from such a system is variable along the orbit, non-thermal X-ray, -ray, and very high-energy -ray emission during the periods of pulsar passing through the dense regions of the companion wind.

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